Despite an emphatic loss in Tuesday's election, backers of Proposition F will continue their long-running effort to drain San Francisco's Hetch Hetchy Reservoir and restore a once-pristine slice of Yosemite National Park.

"We went into this election knowing we'd probably lose," said Mike Marshall, executive director of Restore Hetch Hetchy, which put the initiative on the ballot. "One goal was to win, sure, but also to build a political infrastructure in the city, educate voters about where their water comes from and create a debate about restoring Hetch Hetchy."

In upcoming months, Marshall's organization is planning a legal attack on the city's use of the Hetch Hetchy facility, as well as environmental challenges to the reservoir. The group also has supported efforts to have Congress rescind its 1913 decision to allow the dam to be built in the national park.

"We never put all our eggs in one basket, especially with this initiative," Marshall said.

It's tough for Prop. F supporters to be upbeat about the election results, however.

Unofficial results show Prop. F, which would have required the city to spend $8 million to develop a plan for replacing the water and power that would be lost if Hetch Hetchy was drained, collected only about 23 percent of the vote. It was resoundingly rejected in every neighborhood of San Francisco and is leading in only one of the city's 596 precincts, Number 9741, which includes San Francisco State University.

"It was a good win," said P.J. Johnston, spokesman for the opponents. "That 77 percent is pretty definitive and hopefully should put to rest any serious attempt to drain the reservoir, at least in San Francisco."

But he said there is little the city can do to stop legal and political challenges beyond the ballot box.

"The backers of Prop. F are true believers, and it's a cause for them," he said.

Despite the landslide result, there were some nervous moments for opponents of the measure, Johnston said. Throughout the campaign, backers of Prop. F played down the possibility of destroying O'Shaughnessy Dam and draining the reservoir, saying that even if the measure was approved, a second vote would be needed in 2016 before any action could be taken.

"We were afraid that voters would see this simply as an environmental measure and vote for it," Johnston said. "Our job was to make sure people knew this was about draining Hetch Hetchy Reservoir."

Powerful opposition

The anti-Prop. F forces pulled together a list of opponents that included Mayor Ed Lee, all 11 members of the Board of Supervisors, political leaders like Sen. Dianne Feinstein, D-Calif., and House Minority Leader Nancy Pelosi, D-San Francisco, every living ex-mayor and the city's business community. They all argued that Hetch Hetchy is desperately needed to keep the water flowing to 2.5 million customers in San Francisco and the Bay Area.

"'Yosemite Restoration' sounds harmless enough," Johnston said. "We needed to show that everyone in San Francisco was against it."

That political pile-on went well beyond fair play, Marshall said. The ballot description approved by a city committee, the controller's statement on the financial impact of the measure and even the ballot arguments were all slanted against Prop. F, he added.

"We had the whole election apparatus against us," Marshall said. "I was naive and didn't believe the city would cheat."

Not a total loss

Even in defeat, it looks as if Prop. F backers will get some of what they were looking for.

The city just started using recycled water at Harding Park golf course and has other recycling efforts ready to go, along with plans to increase conservation and make better use of ground water, said Tyrone Jue, a spokesman for the San Francisco Public Utilities Commission.

"We spent $8 million to irrigate 175 acres at Harding Park that we could have spent on another study" under Prop. F, he said.

But Marshall's group, which was founded in 1999, exists to restore the Hetch Hetchy Valley to its original state, and Tuesday's election didn't change that focus.

"We're in the process of preparing a lawsuit that will be filed next year," Marshall said, although he declined to provide details. His group is also pushing to have the Federal Energy Regulatory Commission study environmental alternatives to the Hetch Hetchy Reservoir as part of their relicensing of the power facilities downstream at Don Pedro Dam.

The Prop. F vote was no more than a temporary setback, a beginning, not an end, Marshall argued.

"We're not going to give up on San Francisco," he said. "All we need is 50 percent of the vote, and it looks like we'll get 25 percent this time, so we're halfway there."